This invention relates to a point of sale printer of the type generally employed in the retail industry or in the restaurant industry.
Typically, the point of sale printer is a relatively small device utilizing impact or ink jet printing technology to produce a sales slip and cash receipt. In many of these printers the recording substrate is supplied from a spool which must be threaded through a feed path that transports the substrate through a printing station into a readout station where the image bearing section of the substrate is either automatically or manually separated from the spool.
Although the substrate upon which the receipt is printed can take many forms, it will herein be referred to as paper with the understanding that any type of support material such as heat sensitive or thermal paper that is known and used in the art can be employed in the practice of the present invention.
In busy restaurants or stores, the paper supply must be replaced at relatively short intervals. Replacing the spool has been a time consuming process because in many of the older printers, the leading edge of the paper strip must be hand-fed through the paper path and the feeding mechanism. Hand feeding in many cases cannot only be a time consuming and tedious process, but can also cause the paper to become misaligned in the feed mechanism whereupon the entire paper loading process must be repeated. This, of course, causes further delays and customer dissatisfaction.
In U.S. Pat. No. 5,579,043 to Patry, there is disclosed a small thermal printer that is designed to eliminate some of the problems associated with hand loading a spool of paper into a small printer. As disclosed in this patent, the thermal print head along with the drive motor and the main drive gear are mounted upon the fixed chassis of the machine. The print head coacts with a paper drive roll that is driven through a driven gear that meshes with the main drive gear to transport paper through the printing station. The drive roll, along with a spring loaded cutting blade is mounted in the cover of the machine. When the cover is raised to an open position, the drive roll is pulled away from the printing head along with the cutting blade and the drive roll gear is separated from the main drive gear. In effect, opening the cover of the machine separated the path through the printing station and cut off station along the line of travel of the paper. Accordingly, a new spool of paper can be drop loaded into the paper bin of the machine and the leading edge of the spool drawn over the printing head into the read out station. The cover is then closed over the leading edge of the paper thereby preparing the machine to begin a printing cycle.
Although the Patry device eliminates many of the problems associated with hand loading a paper spool into a printer, it nevertheless creates other problems. Separating the drive roll gear from the main drive gear of the drive system when the cover is opened can produce misalignment of the gear teeth so they will not properly mesh when the cover is closed. This, in turn, can cause undue stress on the drive system leading to early failure. In operation, the drive roll in turn is supported in biasing contact against a row of heating points mounted in the print head. The drive roll thus is constantly driven against the print head as the cover is opened and closed, which can damage the print head and again produce further misalignment of parts. Similarly, separating the cutting blade of the printer during the reloading of a spool can cause further alignment problems.